A process for the preparation of a binder comprising a heterocondensate of (i) a hydrolysable silicon compound having at least one nonhydrolysable organic radical without polymerizable group and (ii) a metal and/or boron compound. The process comprises hydrolyzing (i) with water, adding (ii) to the resultant reaction mixture after the water in the reaction mixture is substantially consumed, and, optionally, adding an organic binder component to the heterocondensate and/or a precursor thereof.